Mild water restriction with or without urea for the longterm treatment of syndrome of inappropriate antidiuretic hormone secretion (SIADH): Can urine osmolality help the choice?

BACKGROUND: Treatment options for chronic SIADH include water restriction (WR) and urea. The usefulness of urine osmolality to guide the choice of the treatment option is not clearly defined. We hypothesized that urine osmolality can indicate whether treatment with mild water restriction alone could be successful. METHODS: Retrospective Review of clinical and biochemical (blood and urine) data of patients with chronic SIADH treated for at least one year with mild WR (1.5-2l/day) either with or without urea. RESULTS: Twenty nine patients were included. Nine patients were treated by mild WR. Mean serum sodium (SNa) and mean Uosm were 129±2mEq/l and 274±78mOsm/kgH2O respectively before WR, and increased to 138.5±3mEq/l and 505±87mOsm/kgH2O (P<0.001). Eight patients were treated with mild WR and 15g urea daily, the SNa and Uosm before treatment were 127.5±3mEq/l and 340±100mOsm/kgH2O respectively and increased to 136.5±1mEq/l and 490±151mOsm/kgH2O (P<0.001). Four of the eight patients had a permanent low solute intake which contributed to hyponatremia. Twelve patients needed 30g urea daily combined with mild WR. The SNa and Uosm were respectively 126±2mEq/l and 595±176mOsm/kgH2O and increased to 136.5±2mEq/l and 698±157mOsm/kgH2O (P<0.05). Uosm increased in most of the treated patients. CONCLUSIONS: About 30% of patients could be treated by moderate WR alone. All these patients presented an initial urine osmolality lower than 400mOsm/kgH2O.

Mild hyponatremia and risk of fracture in the ambulatory elderly.

BACKGROUND: Mild hyponatremia is the commonest electrolyte imbalance in the older population and has been shown to be associated with gait and attention deficits resulting in higher frequency of falls. The association of mild hyponatremia and bone fracture is still unknown. OBJECTIVE: To determine if mild hyponatremia is associated with increased risk of bone fracture in ambulatory elderly. DESIGN, SETTING AND PARTICIPANTS: Case control study of 513 cases of bone fracture after incidental fall in ambulatory patients aged 65 or more in general university hospital. Controls were age and sex matched randomly selected ambulatory patients without history of bone fracture. MAIN EXPOSURE MEASURES: Odds ratio (OR) of bone fracture after incidental fall associated with presence of hyponatremia. RESULTS: Prevalence of hyponatremia (serum sodium <135 mEq/l,) in patients with bone fracture and in controls patient was, respectively, 13.06% and 3.90%. Hyponatremia was mild and asymptomatic in all patients (mean serum sodium 131 mEq/l) and was found to be associated with bone fracture after incidental fall in ambulatory elderly (unadjusted OR: 3.47, 95% CI: 2.09-5.79, and adjusted OR: 4.16 95% CI: 2.24-7.71). Hyponatremia was either drug induced (36% diuretics, 17% selective serotonin reuptake inhibitors) or resulted from idiopathic syndrome of inappropriate antidiuretic hormone secretion (37%). Hyponatremia was associated with 9.20% of all bone fractures. CONCLUSION: Mild asymptomatic hyponatremia is associated with bone fracture in ambulatory elderly and avoiding iatrogenic hyponatremia or treating hyponatremia may decrease the number of bone fractures in this population.